The anatomy and physiology of centrally acting peptides are being studied. These include precursors and derivatives of the opiocortin series (31K, 16K, beta-lipotropin, 7.5K-ACTH, 4.5K-ACTH, -MSH, and the endorphins). Other central peptides under study include LRF, SRIF, TRF, enkephalin and Substance P. Progress continues on the identification and characterization of a nicotine-like peptide of pituitary origin and anti-LRF and anti-TRF substances from the pineal gland. An opiate receptor complex has been isolated and studies are in progress to develop an anti-receptor antiserum for immunochemical and immunohistological purposes.